Bovine parainfluenza virus type 3 (BPIV3) is one of the most important known viral respiratory pathogens of both young and adult cattle. It is also named “heat stress in transport”, causing morbidity and mass death. New variants of BPIV3 have been detected or isolated in China since 2008. Here, we isolate one BPIV3 strain (named BPIV3 BJ) in Madin-Darby bovine kidney (MDBK) cells from nasal samples collected in China. Phylogenetic analysis showed that our isolate is related to BPIV3 of the genotype A. The comparison of BPIV3-BJ and the reference Chinese isolate NM09 showed that these strains are highly divergent. We found many differences in the amino acid composition in the nucleocapsid (NP) protein among these genotype A strains. Since the NP protein has been implicated in immunization studies, our BPIV3 isolate will be useful for the development of immune assays and vaccine studies. The diversity of BPIV3 lineages that we found in China indicated ongoing evolution for immune escape. Our study highlights the importance of genetic surveillance for determining the effect of BPIV3 variability on pathogen evolution and population-scale immunity.

Clostridium butyricum (C. butyricum) is increasingly being used to test the promotion of the gut health of animals. However, the modes of action for such applications for waterfowl remain unclear. Thus, we investigated whether or not intestinal barrier function, immune-related gene expression, and the diversity of the intestinal microbiota in Pekin ducks varied under C. butyricum supplementation. A total of 500 ducks were randomly assigned into five treatments supplemented with basal diets containing: either 0 (group Control), 200 (group CB200), 400 (group CB400) and 600 (group CB600) mg/kg C. butyricum or 150 mg/kg aureomycin (group A150) for 42 days. In comparison with the control group, C. butyricum supplementation enhanced the growth performance and intestinal villus height of Pekin ducks at 42 d. Serum immune indexes and fecal short-chain fatty acids (SCFAs) were all improved at both 21 d and 42 d after C. butyricum addition. The mRNA expression levels of Mucin2, Zonula occludens-1 (ZO-1), Caudin-3, and Occludin increased at 21 d and 42 d and the mRNA expression levels of IL-4 and IL-10 only increased at 42 d after C. butyricum addition. Dietary C. butyricum also resulted in an increase in the number of diversities of operational taxonomic units (OTUs), and an increase in the α-diversity of intestinal microbiota. The addition of C. butyricum altered the composition of the intestinal microbiota from 21 d to 42 d. The relative abundance of Firmicutes and Bacteroidetes showed little changes among groups; however, the relative abundance of Firmicutes/Bacteroidetes were found to have been significantly different between the 21 d and 42 d. C. butyricum administration improved the intestinal health of Pekin ducks by increasing the diversity of intestinal microbiota, enhancing the SCFAs contents, and strengthening the intestinal barrier function and immune systems. The optimal dietary supplementation dosage was recommended as 400 mg/kg in the diet.

Clostridium butyricum (C. butyricum) can attenuate oxidative stress, inflammation, and hepatic fatty deposition in poultry, however, the underlying mechanisms for this in Pekin ducks remain unclear. This study evaluated these hepatoprotective effects and the underlying mechanisms in a corticosterone (CORT)-induced liver injury model in Pekin ducks fed a C. butyricum intervention diet. A total of 500 Pekin ducks were randomly divided into five groups: one group (CON group) was only provided with a basal diet, three groups were provided a basal diet with 200 mg/kg (LCB group), 400 mg/kg (MCB group), or 600 mg/kg (HCB group) C. butyricum, respectively, and one group was provided a basal diet with 150 mg/kg aureomycin (ANT group) for 42 d. At 37 days-old, all ducks received daily intraperitoneal injections of CORT for five days to establish a liver injury model. C. butyricum intervention alleviated liver injury by decreasing the liver organ indices, hepatic steatosis and hepatocyte necrosis, and improving liver function, antioxidant capacity, and inflammatory factors. Hepatic RNA-seq revealed 365 differentially expressed genes (DEGs) between the MCB and CON groups, with 229 up- and 136 down-regulated DEGs in the MCB group. Between the MCB and ANT groups, 407 DEGs were identified, including 299 up- and 108 down-regulated genes in MCB group. Some DEGs in the MCB group related to oxidative stress and inflammatory responses such as Sod3, Tlr2a/b, and Il10, which were up-regulated, while Apoa1, Cyp7a1, Acsl1/5, Fasn, Ppar-γ, and Scd, which are involved in lipid metabolism, were down-regulated, indicating that these genes were responsive to dietary C. butyricum for the alleviation of corticosterone-induced hepatic injury. Toll-like receptor signaling, PI3K-Akt signaling pathway, cytokine-cytokine receptor interaction, peroxisome proliferator-activated receptor (PPAR) signaling pathway, adipocytokine and glycerophospholipid metabolism signaling pathway were significantly enriched in the MCB group. These findings indicate that C. butyricum intervention can protect Pekin ducks from corticosterone-induced liver injury by the modulation of immunoregulatory- and lipid metabolism-related genes and pathways.

Goose astrovirus (GoAstV) infection has become prevalent in major goose-producing regions, causing substantial economic losses to the industry. In this study, an indirect competitive ELISA (ic-ELISA) was developed based on a monoclonal antibody (mAb) targeting the GoAstV VP27 protein. The recombinant VP27 protein was expressed in E. coli and purified, followed by the generation of murine mAbs using the purified antigen. Through screening with GoAstV particles, mAb 3G11 exhibited strong immunoreactivity, which was further confirmed by Western blot and immunofluorescence assay (IFA). The ic-ELISA conditions were optimized as follows: GoAstV particle coating concentration of 10⁴ TCID₅₀ per well, 3G11 mAb dilution of 1:8000, and incubation times of 120 min for coating, 60 min for serum samples, and 60 min for mAb binding. The assay exhibited satisfactory performance in terms of sensitivity, specificity, and reproducibility. Using this method, serum samples collected from major goose farming areas in Shandong province were tested and showed an overall seropositivity rate of 11.7%. This study provided a reliable serological tool for detecting GoAstV-specific antibodies and would support future vaccine evaluation efforts.

Goose astrovirus (GoAstV) infection has become prevalent in major goose-producing regions, causing substantial economic losses to the industry. In this study, an indirect competitive ELISA (ic-ELISA) was developed based on a monoclonal antibody (mAb) targeting the GoAstV VP27 protein. The recombinant VP27 protein was expressed in E. coli and purified, followed by the generation of murine mAbs using the purified antigen. Through screening with GoAstV particles, mAb 3G11 exhibited strong immunoreactivity, which was further confirmed by Western blot and immunofluorescence assay (IFA). The ic-ELISA conditions were optimized as follows: GoAstV particle coating concentration of 10⁴ TCID₅₀ per well, 3G11 mAb dilution of 1:8000, and incubation times of 120 min for coating, 60 min for serum samples, and 60 min for mAb binding. The assay exhibited satisfactory performance in terms of sensitivity, specificity, and reproducibility. Using this method, serum samples collected from major goose farming areas in Shandong province were tested and showed an overall seropositivity rate of 11.7%. This study provided a reliable serological tool for detecting GoAstV-specific antibodies and would support future vaccine evaluation efforts.